Suspended ceiling systems, including exposed metal grid systems for lay in panels and systems utilizing metal hook-on type panels, are extensively used in private and commercial buildings. Such ceiling systems are suspended from the building structure and provide a substantially uninterrupted planar ceiling appearance. Lighting fixtures, air handling vents and the like are often incorporated at various locations in the system.
Conventional suspended ceiling systems which utilize metal panels often include supporting grid elements structured to grip the upstanding edges of the metal panels. Ceiling systems utilizing metal panels have application to buildings that have large ceiling areas or high access areas. These systems are most frequently used in corridors, lobbies, entryways, and hospitality and retail spaces. The metal panels come in widths of varying sizes, are completely accessible and fully conceal the suspension system. The panels provide downward accessibility, requiring minimum plenum clearance.
In geographical regions subject to earthquakes, buildings are designed with lateral force resisting systems, i.e. seismic systems, to resist the effects of earthquake forces. Seismic systems make a building stiffer against horizontal forces, thus minimizing the amount of relative lateral movement and resultant damage. Although the buildings may be designed structurally to provide seismic resistance to lateral forces, the ceiling panels suspended adjacent the trim or border of the ceiling system remain very susceptible to displacement under severe environmental conditions. Thus, the connection of the wall or partition to the ceiling system, ceiling system members and their connections must be designed to support the reaction force of the wall or partition from prescribed loads applied perpendicular to the wall or partition during a seismic event.
FIGS. 1 and 2 illustrate a suspended asymmetric ceiling system which is typically utilized in areas subject to seismic disturbances. The panels positioned adjacent the wall, herein referred to as border panels, are supported by metal L-beam members, often referred to as wall angles, which are fastened to the wall with nails or screws. In this known configuration, the status of the border panels is partially dependent on the status of the wall or partition. By way of example, if the wall to which the wall angle is secured were to be collapse, the border panels supported by the wall angle would fall, potentially injuring people in the room below. Accordingly, there is a need for a ceiling system which secures border panels from unintended displacement. It is also desirable to allow for the border panels to be accessible as usual for installation and de-installation.
Also, island, or floating, ceiling systems, in which the termination of the ceiling plane stands proud of the wall, are in increasing demand as such systems provide an architect with substantially unlimited aesthetic variations in a ceiling system.